Powertrain, generic · Hybrid propulsion

P0BF4 Drive Motor B Phase U Current Sensor Circuit High

Check engine lightOn

EmissionsRelevant

Drive cycleNot required

Limp modePossible

P0BF4 is the upper-limit counterpart of P0BF3 for the phase U current sensor of drive motor B. GM's thresholds: above 800 A on the 2011 Volt, checked with PWM output disabled (Type A); above 700 A on the 2012 and 2013 two-mode trucks (Type B, two trips); above 700 A for 0.05 of 0.1 s in the 2016 tables and 0.1 of 0.15 s in a 2019 table (Type A, one trip). Because the test runs with the power stage idle or the value lies far beyond any real current, it points to the sensor, its supply or an open reference rather than to genuine overcurrent; GM reports real excess phase current of motor B separately under P0C04 (above 600 A in the 2016 and 2019 tables). Motor B output is limited until repair.

Likely causes

Failed phase U current sensor in the motor B inverter

Sensor signal shorted to the sensor supply voltage or open reference ground

Poor contact at an internal or external inverter connector

Symptoms

Malfunction indicator lamp and hybrid warning
Reduced power from drive motor B
Further inverter or phase current codes stored

Repair estimate

DifficultyShop_onlyWorkshop job

Parts and labour€150–4,000

Time1–6 h

Typical range across vehicles; the real cost depends on what the testing finds.

Parts involved

drive motor b phase u current sensorwiring harnesshybrid control module

References: gsi.ext.gm.com, gsi.ext.gm.com, gsi.ext.gm.com, gsi.ext.gm.com.